JP5237733B2 - MEMS sensor - Google Patents

Description

  The present invention relates to a MEMS sensor formed by finely processing a silicon layer, and more particularly to a MEMS sensor that is thin and has an excellent sealing function in a movable region.

  In a MEMS (Micro-Electro-Mechanical Systems) sensor, a movable electrode part and a fixed electrode part are formed by finely processing a silicon (Si) wafer constituting an SOI (Silicon on Insulator) layer. This fine sensor is used as an acceleration sensor, a pressure sensor, a vibration gyro, a micro relay, or the like depending on the operation of the movable electrode portion.

  In this type of MEMS sensor, it is necessary to seal the movable region of the movable electrode portion so that the movable electrode portion formed of a part of the silicon wafer can operate at a fine distance in a clean space.

As a packaging technique for that purpose, in the invention described in Patent Document 1 below, a movable electrode portion and a fixed electrode portion formed from a silicon wafer constituting an SOI layer are disposed between a glass substrate and a glass substrate. The upper and lower glass substrates are joined by glass frit at the peripheral portion of the movable region of the movable electrode portion, and a seal layer is formed by the glass frit.
JP 2000-307018 A

  However, as described in Patent Document 1, in the packaging structure in which the movable electrode portion is sealed between two glass substrates, the thickness dimension of the entire sensor is increased.

  In addition, since the facing distance between the upper and lower glass substrates is determined by the thickness of the glass frit that seals the periphery of the movable region of the movable electrode portion, it is difficult to determine the facing distance between the glass substrates with high accuracy. It is difficult to set a movable margin (margin) necessary for the operation of the movable electrode with an appropriate dimension between the movable electrode portion and the glass substrate.

  Further, since the glass frit is melted and solidified to form a seal layer, it is difficult to form a fine pattern seal layer. Further, in order to prevent the molten glass frit from flowing into the movable region of the movable electrode, it is necessary to provide a distance between the movable region of the movable electrode and the sealing layer of the glass frit. Therefore, the entire packaging must be large.

  Further, in order to reduce the size of this type of MEMS sensor, an electrode layer and a lead layer must be formed in a portion overlapping the movable region of the movable electrode portion. However, the electrode layer, the lead layer, the movable electrode layer, In this case, it is necessary to secure a dimension as a margin, and it is difficult to realize a thin packaging.

  The present invention solves the above-described conventional problems, and is a thin and small-sized MEMS sensor, and has a structure in which an appropriate movable margin (margin) is easily secured between the movable electrode portion and the substrate. The purpose is to provide.

  Another object of the present invention is to provide a MEMS sensor having a structure in which the seal layer surrounding the movable region of the movable electrode portion can be formed thin and the material forming the seal layer does not adversely affect the operation of the movable electrode portion. .

The present invention relates to a MEMS sensor having a first substrate, a second substrate, and a movable electrode portion and a fixed electrode portion disposed between the first substrate and the second substrate.
The surface of said first substrate, and each of the supporting conducting portions of the movable electrode portion and the fixed electrode portion, and the frame layer surrounding said fixed electrode portion and the movable electrode portion, through the first insulating layer is fixed Te,
Convex portions and concave portions are formed on the surface of the second substrate, a second insulating layer is formed on the convex portions and the concave portions, and the second substrate is formed on the surface of the second insulating layer. A convex portion and a concave portion that follow the convex portion and the concave portion are formed,
A connection electrode portion having a thickness greater than 0 μm and 4 μm or less is provided on the surface of the convex portion of the second insulating layer, and the connection electrode portion and a connection provided on the surface of each of the support conduction portions The metal layer is formed by eutectic bonding or diffusion bonding, and the surface of the concave portion of the second insulating layer is opposed to the movable electrode portion, and is formed to surround the movable electrode portion and the fixed electrode portion. A seal electrode portion is provided on the surface of the convex portion of the insulating layer of 2, and the seal electrode portion and the seal metal layer provided on the surface of the frame body layer are eutectic bonded or diffusion bonded ,
A lead layer connected to the connection electrode portion is embedded in the second insulating layer, and the lead layer is routed along the surface of the concave portion and the surface of the convex portion of the second substrate. The second substrate passes between the convex portion of the second substrate and the sealing metal layer and protrudes to the outside of the frame layer .

  The MEMS sensor of the present invention includes a movable electrode portion and a fixed electrode between a first insulating layer provided on the surface of the first substrate and a second insulating layer provided on the surface of the second substrate. The supporting conduction part of the part is sandwiched and fixed. The distance between the first substrate and the second substrate is mainly determined by the thicknesses of the movable electrode portion and the fixed electrode portion and the thicknesses of the first insulating layer and the second insulating layer. Since these thickness dimensions can be set with relatively high accuracy, the thickness dimensions of the first substrate and the second substrate can be determined uniformly, and the entire configuration can be made thin.

  Further, a convex portion and a concave portion are formed on the second substrate, a second insulating layer is formed so as to follow the convex portion and the concave portion, and the concave portion on the surface of the second insulating layer is opposed to the movable electrode portion. Therefore, a movable margin (margin) can be secured between the movable electrode portion and the second insulating layer, and a MEMS sensor that can operate the movable electrode portion reliably while being thin can be obtained.

  The present invention can be configured such that the second insulating layer is formed in the same thickness in the convex portion and the concave portion.

  Since the convex portion and the concave portion are formed on the surface of the second substrate, even if the second insulating layer is formed to have a uniform thickness, it can move between the movable electrode portion and the surface of the second insulating layer. A margin can be secured. Since the second insulating layer can be formed to have a uniform thickness, it is possible to ensure insulation of the lead layer embedded in the second insulating layer.

  Note that in this specification, the second insulating layer is formed to have the same thickness means that the second insulating layer is formed on the surface of the convex portion and the concave portion of the second substrate by a sputtering process or a CVD process. Later, it means that the surface of the second insulating layer is not particularly cut to form a concave portion. For example, the second insulating layer is formed at the boundary between the convex portion and the concave portion of the second substrate. It includes a state in which it is formed thinner than other regions.

  However, in the present invention, in the part facing the recess of the second substrate, the surface of the second insulating layer may be milled to further process the recess on the surface of the second insulating layer. In this case, it is possible to further secure a movable margin between the movable electrode portion and the second insulating layer by the concave portion on the surface of the second substrate and the concave portion obtained by cutting the surface of the second insulating layer. become.

In the present invention, each of the support conductive portions of the movable electrode portion and the fixed electrode portion and the second insulating layer of the second substrate are joined via the joining layer of the connection electrode portion and the connection metal layer . However, since the thickness dimension of the bonding layer is thin, it is easy to determine the interval between the first substrate and the second substrate through the bonding layer with high accuracy. Further, since the metal thickness of the bonding layer is thin, the metal hardly flows into the movable region of the movable electrode portion.

  Moreover, since the movable margin between the movable electrode portion and the second insulating layer can be secured by the concave portion, the thickness dimension of the bonding layer can be made as thin as possible. By making the bonding layer thin, the movable electrode portion and the fixed electrode portion are less likely to receive thermal stress from the bonding layer. In order to prevent distortion of the movable electrode portion and the fixed electrode portion due to thermal stress, the thickness dimension of the connection electrode portion and the thickness dimension of the bonding layer are preferably 4 μm or less.

  In the present invention, it is preferable that a continuous or discontinuous groove surrounding the bonding layer between the connection electrode portion and the connection metal layer is formed in the support conduction portion.

  When the groove is formed, it becomes easy to prevent the metal constituting the bonding layer from diffusing to the surroundings, and it is easy to prevent the operation of the movable electrode portion from being hindered by the metal layer.

In the present invention , a frame body layer is provided so as to surround the movable region, a frame-like convex portion is formed in the second insulating layer so as to surround the movable region, and the frame portion and the convex portion are opposed to each other. since forming a sealing layer by eutectic bonding or diffusion bonding, a seal structure surrounding the movable region of the movable electrode portion thinner can configure, maintain the distance between the first substrate and the second substrate uniformly be able to. In addition, since the metal material of the seal layer is small, it does not easily flow to the movable region of the movable electrode portion, and even if the seal layer is disposed close to the movable region, the metal material does not adversely affect the operation of the movable electrode portion. . Therefore, it becomes easy to configure in a small size. Furthermore, since the metal layer constituting the seal layer is thin and has a small area, the influence of thermal stress due to the difference in thermal expansion coefficient between the metal layer and the insulating layer can be reduced.

  Further, according to the present invention, the lead layer embedded in the second insulating layer is drawn out to the outside of the seal layer, and a connection pad that is electrically connected to the lead layer is provided on the second substrate. It is what.

  The second insulating layer does not exhibit the function of maintaining the distance between the first substrate and the second substrate, but also exhibits the function of insulating the lead layer and guiding it to the outside. Therefore, the thickness can be reduced, and the lead layer can be reliably insulated and connected to an external electric circuit.

  According to the present invention, the facing distance between the first substrate and the second substrate is determined by the thickness dimensions of the movable electrode portion and the fixed electrode portion, and the thicknesses of the first insulating layer and the second insulating layer. The distance between the first substrate and the second substrate can be easily determined with high accuracy and can be thin.

  Further, since the concave portion is formed on the surface of the second insulating layer, it is possible to obtain a MEMS sensor in which the movable electrode portion operates reliably while being thin. Since the convex portion and the concave portion are formed on the surface of the second substrate, and the second insulating layer is formed so as to follow the convex portion and the concave portion of the second substrate, the second insulating layer is extremely thin. Therefore, the insulation of the lead layer formed inside the second insulating layer can be sufficiently ensured.

  Since the movable electrode portion can be secured by the recess, the connection electrode portion and the bonding layer can be made as thin as possible, and the influence of the thermal stress of the bonding layer on the movable electrode portion and the fixed electrode portion can be reduced.

  In addition, a frame layer is provided around the movable region of the movable electrode portion, and a convex portion is formed on the second insulating layer so as to surround the movable region, so that a facing portion between the frame body layer and the convex portion is formed. Since the sealing layer is formed of the bonding layer, the sealing layer can be made thin, and the metal of the sealing layer is less likely to adversely affect the operation of the movable electrode portion.

  FIG. 1 shows a MEMS sensor according to an embodiment of the present invention, and is a plan view showing a movable electrode portion, a fixed electrode portion, and a frame layer. In FIG. 1, illustration of the first substrate and the second substrate is omitted. 2 is an enlarged view of a portion II in FIG. 1, and FIG. 3 is an enlarged view of a portion III. FIG. 4 is a cross-sectional view showing the entire structure of the MEMS sensor, and corresponds to a cross-sectional view taken along line IV-IV in FIG. FIG. 5 is a cross-sectional view illustrating a method for manufacturing the MEMS sensor. 4 and 5, the arrangement configuration of each layer is upside down.

  As shown in FIG. 4, in the MEMS sensor, a functional layer 10 is sandwiched between a first substrate 1 and a second substrate 2. Each part of the 1st board | substrate 1 and the functional layer 10 is joined via 1st insulating layer 3a, 3b, 3c. In addition, a second insulating layer 30 is provided between the second substrate 2 and the functional layer 10.

As shown in FIG. 5, the first substrate 1, the functional layer 10, and the first insulating layers 3a, 3b, 3c are formed by processing an SOI (Silicon on Insulator) layer. The SOI layer used here is obtained by integrally bonding two silicon wafers with an insulating layer (insulator) which is a SiO ₂ layer interposed therebetween. One silicon wafer of the SOI layer is used as the first substrate 1 and the other silicon wafer is processed to form the functional layer 10.

  The functional layer 10 is formed by separating the first fixed electrode portion 11, the second fixed electrode portion 13, the movable electrode portion 15, and the frame layer 25 from a single silicon wafer. Further, a part of the insulating layer of the SOI layer is removed to form first insulating layers 3a, 3b, 3c separated from each other.

  As shown in FIG. 1, the planar shape of the functional layer 10 is 180 degrees rotationally symmetric with respect to the center (centroid) O, and the vertical direction (Y direction) with respect to a line passing through the center O and extending in the X direction. ).

  As shown in FIG. 1, the first fixed electrode portion 11 is provided on the Y1 side from the center O. In the first fixed electrode portion 11, a rectangular support conducting portion 12 is integrally formed at a position approaching the center O. As shown in FIGS. 4 and 5, the support conductive portion 12 is fixed to the surface 1 a of the first substrate 1 by the first insulating layer 3 a. In the first fixed electrode portion 11, only the support conduction portion 12 is fixed to the surface 1 a of the first substrate 1 by the first insulating layer 3 a, and other portions are connected to the first substrate 1. The insulating layer between them is removed, and a gap with a distance corresponding to the thickness of the first insulating layer 3a is formed between the first substrate 1 and the surface 1a.

  As shown in FIG. 1, the first fixed electrode portion 11 has an electrode support portion 11 a having a certain width dimension extending linearly from the support conducting portion 12 in the Y1 direction. A plurality of counter electrodes 11b are integrally formed on the X1 side of the electrode support portion 11a, and a plurality of counter electrodes 11c are integrally formed on the X2 side of the electrode support portion 11a. FIG. 2 shows one counter electrode 11c. Each of the plurality of counter electrodes 11c extends linearly in the X2 direction, and the width dimension in the Y direction is constant. The plurality of counter electrodes 11c are arranged in a comb-like shape with a certain interval in the Y direction. The other counter electrode 11b extending to the X1 side and the counter electrode 11c extending in the X2 direction have a bilaterally symmetric shape with respect to a line extending in the Y direction through the center O.

  A second fixed electrode portion 13 is provided on the Y2 side from the center O. The second fixed electrode portion 13 and the first fixed electrode portion 11 are symmetrical in the vertical direction (Y direction) with respect to a line extending in the X direction through the center O. That is, the second fixed electrode portion 13 includes a rectangular support conducting portion 14 provided at a position approaching the center O, and an electrode support portion having a constant width dimension extending linearly from the support conducting portion 14 in the Y2 direction. 13a. A plurality of counter electrodes 13b extending integrally from the electrode support portion 13a are provided on the X1 side of the electrode support portion 13a, and a plurality of counter electrodes 13c extending integrally from the electrode support portion 13a are provided on the X2 side of the electrode support portion 13a. Is provided.

  As shown in FIG. 3, the counter electrode 13c extends linearly in the X2 direction, has a constant width dimension, and is formed in parallel with each other at a constant interval in the Y direction. Similarly, the counter electrode 13b on the X1 side also linearly extends in the X1 direction with a constant width dimension, and extends in parallel in the Y direction at constant intervals.

  Also in the second fixed electrode portion 13, only the support conduction portion 14 is fixed to the surface 1a of the first substrate 1 through the first insulating layer 3a. The electrode support part 13a and the counter electrodes 13b and 13c, which are the other parts, have an insulating layer removed from the surface 1a of the first substrate 1, and the electrode support part 13a and the counter electrodes 13b and 13c, A gap having a distance corresponding to the thickness of the first insulating layer is formed between the first substrate 1 and the surface 1a.

  The functional layer 10 shown in FIG. 1 has a movable region inside the rectangular frame layer 25, and in the movable region, a portion excluding the first fixed electrode portion 11 and the second fixed electrode portion 13 is a movable electrode portion. It is 15. The movable electrode portion 15 is formed separately from the first fixed electrode portion 11, the second fixed electrode portion 13, and the frame body layer 25 on the same silicon wafer.

  As shown in FIG. 1, the movable electrode portion 15 has a first support arm portion 16 extending in the Y1-Y2 direction on the X1 side with respect to the center O, and at a position close to the X1 side of the center O. In addition, a rectangular support conducting portion 17 formed integrally with the first support arm portion 16 is provided. The movable electrode portion 15 has a second support arm portion 18 extending in the Y1-Y2 direction on the X2 side with respect to the center O, and the second support arm portion is positioned closer to the X2 side of the center O. A rectangular support conducting part 19 formed integrally with the reference numeral 18 is provided.

  The portion sandwiched between the first support arm portion 16 and the second support arm portion 18 and the portion excluding the first fixed electrode portion 11 and the second fixed electrode portion 13 is the weight portion 20. Yes. The edge portion on the Y1 side of the weight portion 20 is supported by the first support arm portion 16 via the elastic support portion 21 and supported by the second support arm portion 18 via the elastic support portion 23. . The edge portion on the Y1 side of the weight portion 20 is supported by the first support arm portion 16 via the elastic support portion 22 and supported by the second support arm portion 18 via the elastic support portion 24. Yes.

  As shown in FIG. 1, on the Y1 side from the center O, a plurality of movable counter electrodes 20a extending from the X1 side edge of the weight portion 20 to the X2 side are integrally formed, and the X2 side of the weight portion 20 A plurality of movable counter electrodes 20b extending from the edge to the X1 side are integrally formed. As shown in FIG. 2, the movable counter electrode 20b formed integrally with the weight portion 20 is opposed to the side on the Y2 side of the counter electrode 11c of the first fixed electrode portion 11 via a distance δ1 when stationary. ing. Similarly, the movable counter electrode 20a on the X1 side is also opposed to the side on the Y2 side of the counter electrode 11b of the first fixed electrode portion 11 via a distance δ1 when stationary.

  The weight portion 20 is integrally formed with a plurality of movable counter electrodes 20c extending in parallel to the X2 direction from the edge portion on the X1 side on the Y2 side from the center O, and in the X1 direction from the edge portion on the X2 side. A plurality of movable counter electrodes 20d extending in parallel are integrally formed.

  As shown in FIG. 3, the movable counter electrode 20d is opposed to the side on the Y1 side of the counter electrode 13c of the second fixed electrode portion 13 via a distance δ2 when stationary. This is the same between the movable counter electrode 20c on the X1 side and the counter electrode 13b. The opposing distances δ1 and δ2 at rest are designed to have the same dimensions.

  As shown in FIG. 4, the support conduction portion 17 that is continuous with the first support arm portion 16 and the surface 1 a of the first substrate 1 are fixed via the first insulating layer 3 b, and the second support The support conduction part 19 continuing to the arm part 18 and the surface 1a of the first substrate 1 are also fixed via the first insulating layer 3b. In the movable electrode portion 15, only the support conduction portion 17 and the support conduction portion 19 are fixed to the first substrate 1 by the first insulating layer 3b, and other portions, that is, the first support arm portion 16, The second support arm portion 18, the weight portion 20, the movable counter electrodes 20 a, 20 b, 20 c, 20 d and the elastic support portions 21, 22, 23, 24 have an insulating layer between the surface 1 a of the first substrate 1. A gap having an interval corresponding to the thickness dimension of the first insulating layer 3b is formed between these portions and the surface 1a of the first substrate 1.

  The elastic support portions 21, 22, 23, and 24 are formed so as to form a meander pattern with thin plate spring portions cut out from the silicon wafer. As the elastic support portions 21, 22, 23, and 24 are deformed, the weight portion 20 is movable in the Y1 direction or the Y2 direction.

  As shown in FIG. 1, the frame layer 25 is formed by cutting a silicon wafer forming the functional layer 10 into a square frame shape. The first insulating layer 3 c is left between the frame layer 25 and the surface 1 a of the first substrate 1. The first insulating layer 3 c is provided so as to surround the entire outer periphery of the movable region of the movable electrode portion 15.

  The manufacturing method of the functional layer 10 shown in FIGS. 4 and 5 uses an SOI layer in which two silicon wafers are bonded via an insulating layer, and the first fixed electrode portion 11 is formed on the surface of one silicon wafer. A resist layer is formed to cover the second fixed electrode portion 13, the movable electrode portion 15, and the frame layer 25, and a portion of the silicon wafer is exposed at a portion exposed from the resist layer. The first fixed electrode part 11, the second fixed electrode part 13, the movable electrode part 15 and the frame body layer 25 are separated from each other by ion etching means.

  At this time, a large number of fine holes are formed by the deep RIE in all regions except the support conductive portions 12, 14, 17, 19 and the frame layer 25. 2 and FIG. 3 illustrate a minute hole 11d formed in the counter electrode 11c, a minute hole 13d formed in the counter electrode 13c, and a minute hole 20e formed in the weight portion 20.

After etching the silicon wafer by Fukahori RIE or the like, a selective isotropic etching process that can dissolve the SiO ₂ layer of the insulating layer without dissolving the silicon is performed. At this time, the etching gas or the etchant penetrates into the grooves separating the respective parts of the silicon wafer, and further penetrates into the fine holes 11d, 13d, and 20e, and the insulating layer is removed.

  As a result, the first insulating layers 3a, 3b, 3c are left only between the support conductive portions 12, 14, 17, 19, and the frame layer 25 and the surface 1a of the first substrate 1, and the other portions The insulating layer is removed at the portion.

  The first substrate 1 processed using the SOI layer has a thickness dimension of about 0.2 to 0.7 mm, the functional layer 10 has a thickness dimension of about 10 to 30 μm, and the first insulating layers 3a, 3b, The thickness of 3c is about 1 to 3 μm.

  The second substrate 2 is formed of a single layer silicon wafer having a thickness dimension of about 0.2 to 0.7 mm.

  As shown in FIGS. 4 and 5, the surface 2a of the second substrate 2 is formed to be uneven by etching. On the surface 2a, a convex portion 4a facing the support conducting portion 12 of the first fixed electrode portion 11 and a convex portion 4a facing the support conducting portion 14 of the second fixed electrode portion 13 are formed and movable. Protrusions 4 b that face the support conduction portions 17 and 19 of the electrode portion 15 are formed. Furthermore, a quadrangular frame-shaped convex portion 4 c is formed on the surface 2 a so as to surround the outer periphery of the movable region of the movable electrode portion 15. The convex portion 4 c faces the frame body layer 25.

  On the surface 2 a of the second substrate 2, a recess 5 is formed in a region facing at least the weight portion 20 that is the movable portion of the movable electrode portion 15 and the movable counter electrodes 20 a, 20 b, 20 c. The surfaces of all the convex portions 4a, 4b, 4c are located on the same plane.

A second insulating layer 30 is formed on the surface 2 a of the second substrate 2. The second insulating layer 30 is an inorganic insulating layer such as SiO ₂ , SiN or Al ₂ O ₃ and is formed by a sputtering process or a CVD process. As the inorganic insulating layer, a material is selected whose difference in thermal expansion coefficient from the silicon wafer is smaller than the difference in thermal expansion coefficient between the conductive metal constituting the connection electrode portion and the silicon wafer. Preferably, SiO ₂ or SiN having a relatively small difference in thermal expansion coefficient from the silicon wafer is used.

  The second insulating layer 30 is formed with a constant thickness so as to follow the protrusions 4 a, 4 b, 4 c and the recess 5. As a result, the convex portions 37a, 37b, and 37c are formed on the surface of the second insulating layer 30 at the portions that cover the convex portions 4a, 4b, and 4c of the second substrate 2. The convex portion 37 a individually faces the support conductive portion 12 of the first fixed electrode portion 11 and the support conductive portion 14 of the second fixed electrode portion 13, and the convex portion 37 b is the support conductive portion 17 of the movable electrode portion 15. , 19 individually. Further, the convex portion 4 c is formed so as to face the frame body layer 25 and surround the entire circumference of the movable region of the movable electrode portion 15.

  On the surface of the second insulating layer 30, a recess 38 is formed in a portion covering the recess 5. The concave portion 38 is opposed to at least the weight portion 20 that is the movable portion of the movable electrode portion 15 and the movable counter electrodes 20a, 20b, and 20c.

  As shown in FIGS. 4 and 5, on the surface of the convex portion 37 a of the second insulating layer 30, the support conduction portion 12 of the first fixed electrode portion 11 and the support conduction portion 14 of the second fixed electrode portion 13. Connection electrode portions 31 that face each other are formed. In addition, a connection electrode portion 32 facing each of the support conducting portion 17 and the support conducting portion 19 of the movable electrode portion 15 is formed on the surface of the convex portion 37 b of the second insulating layer 30.

  Further, a seal electrode portion 33 is formed on the surface of the convex portion 37 c of the second insulating layer 30 so as to face the surface of the frame body layer 25. The seal electrode portion 33 is formed of the same conductive metal material as the connection electrode portions 31 and 32. The seal electrode portion 33 is formed in a rectangular frame shape so as to face the frame body layer 25, and is formed so as to surround the entire periphery of the movable region of the movable electrode portion 15. The connection electrode portions 31 and 32 and the seal electrode portion 33 are made of aluminum (Al).

  Inside the second insulating layer 30, a lead layer 34 that conducts to one connection electrode portion 31 and a lead layer 35 that conducts to the other connection electrode portion 32 are provided. The lead layers 34 and 35 are made of aluminum. The plurality of lead layers 34 and 35 are individually connected to the connection electrode portions 31 and 32, respectively. Each lead layer 34, 35 passes through the inside of the second insulating layer 30 and crosses the portion where the seal electrode portion 33 is formed without contacting the seal electrode portion 33, so that the seal electrode It extends outside the area surrounded by the portion 33. The second substrate 2 is provided with connection pads 36 that are electrically connected to the lead layers 34 and 35 outside the region. The connection pad 36 is made of aluminum, gold, or the like, which is a conductive material that is low resistance and hardly oxidizes.

  Since the second insulating layer 30 is formed with a certain thickness dimension, and the lead layers 34 and 35 are routed inside the second insulating layer 30, the lead layers 34 and 35 and the second substrate 2 are arranged. Sufficient electrical insulation can be secured. In addition, the lead layers 34 and 35 are not easily exposed to the functional layer 10 side.

  The second insulating layer 30 is formed by forming the protrusions 4a, 4b, 4c and the recess 5 on the surface 2a of the second substrate 2 by an etching process, and then forming an inorganic insulating layer on the surface with a certain thickness. And formed by a sputtering process or a CVD process. Next, lead layers 34 and 35 are formed on the surface by sputtering or the like, and an inorganic insulating layer is formed by a sputtering process or a CVD process so as to cover the lead layers 34 and 35.

  As shown in FIG. 5, a connection metal layer 41 facing the connection electrode portion 31 is formed on the surfaces of the support conductive portions 12 and 14 of the functional layer 10, and on the surfaces of the support conductive portions 17 and 19, A connection metal layer 42 facing each connection electrode portion 32 is formed by a sputtering process. Further, a seal metal layer 43 facing the seal electrode portion 33 is formed on the surface of the frame body layer 25. The seal metal layer 43 is simultaneously formed of the same metal material as the connection metal layers 41 and 42.

  The connection metal layers 41 and 42 and the seal metal layer 43 are made of germanium, which is a metal material that is easily eutectic bonded or diffusion bonded to aluminum forming the connection electrode portions 31 and 32 and the seal electrode portion 33.

  As shown in FIG. 4, the first substrate 1 and the second substrate 2 are overlapped so that the surfaces 1a and 2a face each other, the connection electrode portion 31 and the connection metal layer 41 face each other, and the connection electrode portion 32 and The connection metal layer 42 is made to face, and the seal electrode part 33 and the seal metal layer 43 are made to face each other. And the 1st board | substrate 1 and the 2nd board | substrate 2 are pressurized with a weak force, heating. As a result, the connection electrode portion 31 and the connection metal layer 41 are eutectic bonded, and the connection electrode portion 32 and the connection metal layer 42 are eutectic bonded. Or diffusion bonding. By means of eutectic bonding or diffusion bonding between the connection electrode portions 31 and 32 and the connection metal layers 41 and 42, the support conductive portions 12, 14, 17 and 19 are connected to the first insulating layers 3 a and 3 b and the second insulating layer 30. The connection electrode portions 31 and 31 and the support conduction portions 12 and 14 are individually conducted, and the connection electrode portions 32 and 32 and the support conduction portions 17 and 19 are individually conducted. To do.

  At the same time, the seal electrode portion 33 and the seal metal layer 43 are eutectic bonded or diffusion bonded. By this bonding, the frame layer 25 and the second insulating layer 30 are firmly fixed, and a metal seal layer 45 surrounding the entire periphery of the movable region of the movable electrode portion 15 is formed.

  Since this MEMS sensor has a structure in which an SOI layer in which two silicon wafers are bonded via an insulating layer and another silicon wafer are stacked, the MEMS sensor is thin overall. Further, the support conduction portion 12 of the first fixed electrode portion 11, the support conduction portion 14 of the second fixed electrode portion 13, and the support conduction portions 17 and 19 of the movable electrode portion 15 are formed by the first insulating layers 3a and 3b. And the second insulating layer 30, the support conduction portions 12, 14, 17, and 19 are stably supported and fixed.

  The support conductive portions 12, 14, 17, 19 and the second insulating layer 30 are bonded by eutectic bonding or diffusion bonding of the connection electrode portions 31, 32 and the connection metal layers 41, 42. Is thin and has a small area, and the support conductive portions 12, 14, 17, 19 and the first substrate 1 are joined via the first insulating layers 3a and 3b made of an inorganic insulating material. Therefore, even if the ambient temperature becomes high, the thermal stress of the bonding layer hardly affects the support structure of the support conductive portions 12, 14, 17, and 19, and the fixed electrode portions 11 and 13 and the movable electrode portion 15 due to the thermal stress. It is hard to generate distortion.

  Similarly, the metal seal layer 45 surrounding the movable region of the movable electrode portion 15 is a thin bonding layer formed between the frame body layer 25 and the second insulating layer 30, and the frame body layer 25 is sufficient. Therefore, the first substrate 1 and the second substrate 2 are less likely to be distorted by the thermal stress of the metal seal layer 45.

  This MEMS sensor has an overall thickness dimension of almost the same depending on the thickness dimension of the first substrate 1 and the second substrate 2, the thickness dimension of the functional layer 10, and the thickness dimension of the second insulating layer 30. It is decided. Since the thickness dimension of each layer can be managed with high accuracy, variations in thickness are less likely to occur. Moreover, since the recess 38 is formed in the second insulating layer 30 so as to face the movable region of the movable electrode portion 15, even if the whole is thin, the movable electrode portion 15 has a movement margin in the thickness direction ( Even if a large acceleration in the thickness direction is applied from the outside, the weight portion 20 and the movable counter electrodes 20a, 20b, 20c, and 20d are difficult to hit the second insulating layer 30 and cause a malfunction. Hateful.

  In addition, since the second insulating layer 30 is formed with an integral thickness, the electrical insulation between the lead layers 34 and 35 wired therein and the second substrate 2 can be sufficiently ensured, and the leads It is difficult for the layers 34 and 35 to be exposed on the surface of the second insulating layer 30.

  This MEMS sensor can be used as an acceleration sensor that detects acceleration in the Y1 direction or the Y2 direction. For example, when acceleration in the Y1 direction acts on the MEMS sensor, the weight portion 20 of the movable electrode portion 15 moves in the Y2 direction due to the reaction. At this time, the facing distance δ1 between the movable counter electrode 20b and the fixed counter electrode 11c shown in FIG. 2 increases, and the capacitance between the movable counter electrode 20b and the counter electrode 11c decreases. At the same time, the facing distance δ2 between the movable counter electrode 20d and the counter electrode 13c shown in FIG. 3 becomes narrow, and the capacitance between the movable counter electrode 20b and the counter electrode 13c increases.

  A change in acceleration acting in the Y1 direction is detected by detecting a decrease and an increase in capacitance with an electric circuit and obtaining a difference between an output change due to an increase in the facing distance δ1 and an output change due to a decrease in the facing distance δ2. And the magnitude of acceleration can be detected.

  In the present invention, the weight portion 20 of the movable electrode portion 15 moves in the thickness direction in response to the acceleration in the direction orthogonal to the XY plane, and the counter electrodes 11b, 11c of the fixed electrode portions 11, 13 are moved. , 13b, 13c and the movable counter electrode 20a, 20b, 20c in the movable electrode portion 15 are opposed to each other in the thickness direction of the movable electrode portion 15 to change the facing area. You may detect the change of the electrostatic capacitance between counter electrodes.

  6A and 6B show a MEMS sensor according to a further preferred embodiment of the present invention, which corresponds to an enlarged cross-sectional view of a portion VI in FIG.

  In the embodiment shown in FIG. 6A, a groove 51 is formed on the surface of the support conductive portion 17 of the movable electrode portion 15 so as to surround the joint portion between the connection metal layer 42 and the connection electrode portion 32. The groove 51 may be formed so as to continuously surround the entire peripheral length of the joint portion, or may be formed by being divided into a plurality at intervals so as to surround the joint portion.

  In the embodiment shown in FIG. 6B, a groove 52 is formed on the surface of the support conductive portion 17 of the movable electrode portion 15 so as to surround the joint portion between the connection metal layer 42 and the connection electrode portion 32. The groove 52 is continuously formed around the joint, and a part of the joint metal layer 42 is formed up to the inside of the groove 52.

  In the embodiment shown in FIGS. 6A and 6B, the molten metal is blocked by the grooves 51 and 52 during the eutectic bonding or diffusion bonding of the connection electrode portion 32 and the connection metal layer 42, and the movable electrode portion It is possible to more reliably prevent the fluid from flowing to the movable region of the 15 weight portions 20 and the electrode facing portions shown in FIGS.

  In the above-described embodiment, the connection electrode portions 31 and 32 and the seal electrode portion 33 are aluminum, and the connection metal layers 41 and 42 and the seal metal layer 43 are germanium, but a metal capable of eutectic bonding or diffusion bonding. Examples of the combination include aluminum-zinc, gold-silicon, gold-indium, gold-germanium, and gold-tin. By combining these metals, it becomes possible to perform bonding at a relatively low temperature of 450 ° C. or lower, which is a temperature lower than the melting point of each metal.

FIG. 7 is a cross-sectional view showing a MEMS sensor of a reference example .
In this MEMS sensor, an IC package 100 is used instead of the second substrate 2. The IC package 100 includes a detection circuit that detects a change in capacitance between the counter electrode and the movable counter electrode.

  A convex portion and a concave portion are formed on the upper surface 101 of the IC package 100, and the second insulating layer 30 is formed thereon with a constant thickness. Since the second insulating layer 30 is formed following the convex portions and concave portions of the upper surface 101, convex portions 37 a, 37 b, 37 c and concave portions 38 are formed on the surface of the second insulating layer 30. And the connection electrode parts 31 and 32 and the seal electrode part 33 are formed in the surface of the said convex parts 37a, 37b, 37c. The connection electrode portions 31 and 32 are electrically connected to electrode pads or the like appearing on the upper surface 101 of the IC package 100 through connection layers 134 and 135 such as through holes penetrating the second insulating layer 30, and the IC package 100. It is connected to the electrical circuit inside.

  Also in the MEMS sensor shown in FIG. 7, the functional layer 10 is disposed between the first substrate 1 and the second insulating layer 30, and the second insulating layer 30 is formed by managing the thickness dimension. Therefore, the functional layer 10 can be stably held without protruding significantly from the upper surface 101 of the IC package 100.

FIG. 8 shows a simulation model for obtaining the optimum value of the thickness dimension of the connection electrode portions 31 and 32 or the bonding layer. The first substrate 101, the fixed electrode portion 116, and the first insulating layer 103 are assumed to be processed from an SOI layer. The first substrate 101 and the fixed electrode portion 116 are a silicon wafer, and the first insulating layer 103. Is SiO ₂ . The second substrate 102 is also a silicon wafer, and the second insulating layer 130 is also SiO ₂ . In this simulation, the thermal stress was calculated with the bonding layer 132 as a single layer of aluminum.

The physical property values used for the calculation are as follows.
Young's modulus (N / m ² ): Si was 1.50E + 11, SiO ₂ was 7.20E + 10, and Al was 7.03E + 10.
Poisson's ratio (-): Si was 0.17, SiO ₂ was 0.25, and Al was 0.35.

Thermal expansion coefficient (/ kelvin): Si was 2.60E-06, SiO ₂ was 5.60E-07, and Al was 2.33E-05.

  In addition, the length dimension L1 of the first insulating layer 103 is 70 μm, and the total length dimension of the fixed electrode portion 116 is 350 μm.

  The thicknesses of the first substrate 101 and the second substrate 102 were 100 μm, the first insulating layer 103 was 1.5 μm, the fixed electrode portion 116 was 20 μm, and the second insulating layer 130 was 3 μm.

  The length dimension W0 of the bonding layer 132 was 20 μm, and the thickness dimension T0 of the bonding layer 132 was changed between 0.5 μm and 10 μm. About each, the displacement amount to the (delta) direction of the lower front-end | tip part P1 and the upper front-end | tip part P2 of the fixed electrode part 116 by the thermal stress of the joining layer 132 when heated at 75 degreeC was calculated.

  In FIG. 9, the horizontal axis indicates the thickness T0 of the bonding layer 132 in units (μm), and the vertical axis indicates the displacement amounts of P1 and P2 in units (nm). In FIG. 9, the lower tip portion P <b> 1 is described as “vertex 1”, and the upper tip portion P <b> 2 is described as “vertex 2”.

  9, the thickness W0 of the bonding layer 132 is preferably 4 μm or less, and more preferably 1 μm or less.

  That is, in the embodiment, the thickness dimension of the connection electrode portions 31 and 32 or the thickness dimension of the entire bonding layer is preferably 4 μm or less, and more preferably 1 μm or less.

The top view which shows the separation pattern of the movable electrode part of the MEMS sensor of embodiment of this invention, a fixed electrode part, and a frame body layer, FIG. FIG. It is sectional drawing which shows the laminated structure of a MEMS sensor, and is equivalent to sectional drawing in the IV-IV line of FIG. Sectional drawing which shows the manufacturing method of a MEMS sensor, (A) (B) is the expanded sectional view which shows the detail of the structure of the VI arrow part of FIG. 4 according to embodiment, Sectional drawing which shows the reference example which used IC package instead of the 2nd board | substrate, An explanatory diagram of a simulation model for obtaining the optimum value of the thickness of the connection electrode part or the bonding layer, Diagram showing simulation results,

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st board | substrate 2 2nd board | substrate 3a, 3b, 3c 1st insulating layer 4a, 4b, 4c Convex part 5 Concave part 10 Functional layer 11 1st fixed electrode part 12 Support conduction | electrical_connection part 11b, 11c Counter electrode 13 1st 2 fixed electrode parts 14 support conduction parts 13b, 13c counter electrode 15 movable electrode part 16 first support arm part 17 support conduction part 18 second support arm part 19 support conduction part 20 weight parts 20a, 20b, 20c, 20d Movable counter electrode 21, 22, 23, 24 Elastic support portion 25 Frame layer 30 Second insulating layer 31, 32 Connection electrode portion 33 Seal electrode portion 37 a, 37 b, 37 b Protrusion portion 38 Recess portion 41, 42 Connection metal layer 43 Seal Metal layer 45 Metal seal layer 100 IC package

Claims (5)

In a MEMS sensor having a first substrate, a second substrate, and a movable electrode portion and a fixed electrode portion disposed between the first substrate and the second substrate,
The surface of said first substrate, and each of the supporting conducting portions of the movable electrode portion and the fixed electrode portion, and the frame layer surrounding said fixed electrode portion and the movable electrode portion, through the first insulating layer is fixed Te,
Convex portions and concave portions are formed on the surface of the second substrate, a second insulating layer is formed on the convex portions and the concave portions, and the second substrate is formed on the surface of the second insulating layer. A convex portion and a concave portion that follow the convex portion and the concave portion are formed,
A connection electrode portion having a thickness greater than 0 μm and 4 μm or less is provided on the surface of the convex portion of the second insulating layer, and the connection electrode portion and a connection provided on the surface of each of the support conduction portions The metal layer is formed by eutectic bonding or diffusion bonding, and the surface of the concave portion of the second insulating layer is opposed to the movable electrode portion, and is formed to surround the movable electrode portion and the fixed electrode portion. A seal electrode portion is provided on the surface of the convex portion of the insulating layer of 2, and the seal electrode portion and the seal metal layer provided on the surface of the frame body layer are eutectic bonded or diffusion bonded ,
A lead layer connected to the connection electrode portion is embedded in the second insulating layer, and the lead layer is routed along the surface of the concave portion and the surface of the convex portion of the second substrate. The MEMS sensor is characterized in that it passes between the convex portion of the second substrate and the sealing metal layer and comes out of the frame layer .   The MEMS sensor according to claim 1, wherein the second insulating layer is formed to have the same thickness in the convex portion and the concave portion. The support The conductive portion, continuous or discontinuous MEMS sensor grooves claim 1 which is formed of surrounding the bonding layer and the connection metal layer and the connection electrode section. The frame body layer, MEMS sensor of claim 1, wherein formed in the same thickness of the same material as the movable electrode portion and the fixed electrode portion. Wherein the two substrates, MEMS sensor of claim 1, wherein the connection pad is provided with the lead layer becomes conductive drawn to the outside of the frame layer.

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